Making sense of sensors: what you don't know your phone knows about you

What do all of the sensors in your phone do, and what's coming in the near future?

Your mobile phone already knows where it is, how you're holding it, what you're saying to it and how fast you're moving.

Yet with significant improvements in mobile sensor technology just around the corner, this is only the beginning chapter in the era of self-aware devices and continuous data logging. There's much more to come.

We're now used to phones and tablets recognising when they're being held upside down and flipping the screen accordingly, but even this kind of technology is a relatively new innovation that has only become commonplace in the last three or four years.

One of the earliest consumer products to showcase these sensors wasn't a phone at all, but the Nintendo Wii games console.

Making sense of sensors

The sensors we've grown accustomed to, and which you can find in almost every new device on the market, include the accelerometer, for measuring movement and orientation, and the gyroscope, for measuring angular rotation across three axes and giving more accuracy to the accelerometer reading.

Location services are taken care of with a magnetometer for detecting magnetic North and some form of GPS chip or a related variant to plot your position on the map.

On top of this there's the proximity sensor for recognising when you move your phone up to your face during a call and an ambient light sensor for boosting brightness levels in dark environments.

Show me the way to go home... thanks to GPS

Like every electrical component, these sensors continue to get smaller, more powerful and cheaper. The total cost of all the sensors inside your brand new mobile phone is probably less than a handful of pounds, though as with any other hardware there are budget and premium options available.

The list price of the accelerometer in the new iPhone, for example, is $1. Whatever the cost, they've become an integral part of the mobile experience: imagine a tablet that doesn't change orientation when you rotate it, or a phone that can't give you directions back home.

The cutting edge

As 2013 draws to a close, there are yet more sensors marking their ground. Apple's iPhone 5S and iPad Air come with an M7 tracking chip, which adds to the motion sensing capabilities of these devices. In practice, it can tell the difference between walking and driving, and take certain actions (such as switching off Wi-Fi) if you haven't moved for a while.

If you're on a train, the M7 chip can be used to tell the phone to stop trying to attach to public networks as they whizz by. Fitness apps, meanwhile, can access accurate data about your movements with no need for a wristband.

Samsung isn't shy of throwing everything it can into a handset, and this is certainly the case when it comes to the sensors packed into both the Galaxy S4 and Galaxy S5 handsets.

These phones includes both temperature and humidity sensors, the data for which you can access through the S Health app, enabling the phone to keep an eye on the state of the environment around you.

There's also a barometer for measuring atmospheric pressure and a gesture sensor that detects hand movements through infrared rays.

There are no less than 9 sensors packed into the Galaxy S4.

So much for the here and now: what about the months and years to come? In short, more sensors and greater accuracy.

We spoke to Emiliano Miluzzo, Senior Member of Technical Staff at US mobile giant AT&T, to get an insight into what could come next. As part of his role at AT&T Labs Research, he specialises in mobile sensing systems and big data analysis. "The trend of adding more sensors to mobile devices will continue," says Miluzzo.